Results 1 - 10 of 2296
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[en] Surface enhancement to prevent wear, self welding, thermal shock stress and irradiation attack is obtained by applying spray coatings performed by the detonation gun process. The equipment and the process are described and density hardness, porosity, microstructure and bond strength of the coatings are examined
[en] The aim of present work was principally focus upon development of Mo composite coating using HVOF thermal spray coating process and to enhance residual stresses using Taguchi approach. The process parameter used in Taguchi experiment are Temperature, load and frequency. ANOVA method was used to examine and analyze the process parameters significance of Mo composite coating. The HRXRD and FESEM attached EDS were used to confirm surface morphology and presence of Mo based composite coating on steel substrate. Experimental results also concluded that for percent (%) change in residual stress, temperature (64.19%) has maximum % contribution followed by frequency (21.82%) and load (6.31%). (paper)
[en] In this study, numerical analysis is performed to adopt the equivalence ratio on the high velocity oxygen fuel (HVOF) thermal spray coating systems equipped with a minimum length nozzle. The analysis is applied to investigate the axisymmetric, steady-state, turbulent, and chemically combusting flow both within the torch and in a free jet region between the torch and the substrate to be coated. The combustion is modeled using a single-step and eddy-dissipation model which assumes that the reaction rate is limited by the turbulent mixing rate of the fuel and oxidant. As the diameter of the nozzle throat is increased, the location of the Mach shock disc moves backward from the nozzle exit. As the throat diameter and the divergent portion are 6 mm and 8 mm, respectively, the pressure in the HVOF system is the lowest at the chamber and the expanding gas is steadily maintained with both high velocity and high temperature for different equivalence ratios. Thus, relatively minor amendments of the equivalence ratio and the geometry of HVOF can lead to improved control over coating characteristics. (low temperature plasma)
[en] Plasma spray coating is the most preferred and readily available method of carrying out repair and restoration works in comparison to other methods at present. Though the method of plasma spraying has been known for a long time, there are still a number of unsolved issues related to the choice of optimal deposition regimes. The thermo-electric plasma system for plasma spray coating with a liquid electrode is discussed in this article. The process and optimal parameters of plasma spray coating regimes are described. (paper)
[en] This paper presents the advantages of spray coating technique as compared to the conventional spin coating method for photoresist coating of 3D microstructures. An optimized mix of photoresist AZ4620: MEK: PGMEA (1:1.5:0.5) was used to achieve good coverage and uniformity of photoresist not only on planar surface, but also along the trenches' sidewall. In order to achieve the ideal coverage of photoresist layer, the effects of the geometries of the microstructures were also considered. Then, we implement this technique for our application in a MEMS device to prove the viability and potentiality of spray coating of photoresist for fabrication of 3D microstructures
[en] Pure copper chosen as substrate was coated with Molybdenum Disulphide (MoS2) through cold spray coating method. A coating thickness of 123 ± 10 μm was obtained while a hardness improvement of 34.5% was obtained on comparing coated over uncoated substrate. Dry sliding wear analysis performed on coated pin specimens by varying process parameters such as applied load (10, 20, 30 N), sliding distance (750, 1250, 1750 m) and sliding velocity (0.75, 1.5 2.25 m s−1) revealed an increasing wear rate trend as applied load increases whereas an initial increase followed by a drastic decrease trend was observed for sliding velocity. Wear decreased initially followed by a slow rise, as sliding distance increases. ANOVA analysis confirmed highest influence for applied load, followed by sliding velocity and sliding distance. Confirmation experiments validated the regression model generated through RSM, which confirmed adequacy of model. For applied load, a wear mechanism transition from mild to severe wear was observed whereas, for sliding distance, the presence of an oxide layer was observed, which makes it suitable for automotive bearings and cylinder liners. (paper)
[en] We study supersonic impact of individual metallic microparticles on metallic substrates, that is, the unit process of materials buildup in cold spray coatings/additive manufacturing. We resolve the moment of impact bonding through real-time observations of single particle impacts with micron-scale and nanosecond-level resolution. We offer the first in-situ observation of a material-dependent threshold velocity, above which the particle undergoes an impact-induced jet-like material ejection and adheres to the substrate. We report direct measurements of critical velocities for structural metals, which unlike in nozzle experiments, are not affected by process-related complexities obscuring particles' kinetic and thermal histories.
[en] The density of thermal sprayed coatings is one of the main factors determining the physical-mechanical properties of the resultant surface layer. The aim of this work is the experimental examination of the statistical characteristics of the local density of the coating, produced by spraying on the rough surface, and comparison of the results of the experiments with the calculations carried out using the proposed model
[en] We demonstrate the fabrication of polymer solar cells in which both a PEDOT:PSS hole transport and a PCDTBT:PC_7_1BM photoactive layer are deposited by spray-casting. Two device geometries are explored, with devices having a pixel area of 165 mm"2 attaining a power conversion efficiency of 3.7%. Surface metrology indicates that the PEDOT:PSS and PCDTBT:PC_7_1BM layers have a roughness of 2.57 nm and 1.18 nm over an area of 100 μm"2. Light beam induced current mapping reveals fluctuations in current generation efficiency over length-scales of ∼2 mm, with the average photocurrent being 75% of its maximum value
[en] In this paper, silver nanowires (AgNWs) with mean diameters of 65 nm and mean length of 9.8 µm were synthesized by the polyol solvothermal method. Sonication-induced scission was used to obtain AgNWs with a length range of 7.1–3.3 µm, and further AgNWs solutions were prepared with as-synthesized AgNWs as conductive fillers in the ethanol. A series of AgNWs random networks were prepared on the glass substrate using spray coating technique. Photoelectric properties and microstructure characterizations of AgNWs random networks were conducted to identify changes in such properties and the extent of these changes as a function of the length and content of AgNWs. The results show the sheet resistance and the transmittance of AgNWs network gradually increase as the length of AgNWs decrease. However, as the concentration of AgNWs increase, the sheet resistance and the transmittance of AgNWs networks decreases and increases, respectively. To obtain an approximative Rs of AgNWs film, the concentration of AgNWs with a length of 7.1 µm should be 1.2 times that of AgNWs with a length of 9.1 µm, with a 10% dropped transmittance. These results are attributed to the increase of the contact resistance among AgNWs networks and the density of AgNWs at the same area coverage. As the concentration of AgNWs increases, the deposition density of AgNWs networks increases, and both the sheet resistance and the transmittance decrease gradually.